Thanks,
I have a Sony DVD RW DRU-510A. Inside, there is what appears to be a round counterweight that fits on top of the disc as it spins to keep the disc on the spindle. This keeps coming off. I didn't notice anything that it attaches to, but you can tell where it fits. It might not really attach to anything as it looks like it spins with the disc. I've placed it back in the spot where it goes and it will work for a day or two and then it comes off. I burn at low speeds and nothing looks damaged.